A Guide to Rare Nacreous Clouds (Polar Stratospheric clouds)

Beautiful, Ethereal Clouds Eating the Ozone Layer

Nacreous clouds are also known as polar stratospheric clouds (PSCs), and can be seen in the polar countries of the northern and southern hemisphere.

These rare and beautiful clouds shimmer with colours you find in a seashell, hence their nickname "mother of pearl clouds".

Despite their beauty, the increasing frequency of nacreous clouds is worrying for scientists. You wouldn't think of such a delicate pretty looking cloud as being destructive, but that's exactly what the mother of pearl cloud is - they are helping to destroy our ozone layer.

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Facts About Nacreous Clouds - How a polar stratospheric cloud is formed

Nacreous clouds form in the Stratosphere, between 10 and 30 miles up. The weather clouds we see everyday form in troposphere, with cirrus clouds being the highest at about 6 miles up. The next layer in our atmosphere is the stratosphere, which is separated from the troposphere by the tropopause.

The stratosphere is very different to the troposphere; it is made up of thin dry air in stable conditions. Also in contrast to the troposphere, the temperature rises from the bottom to the top in the stratosphere, which is caused by the absorption of heat from the ozone layer.

Nacreous clouds seen in the polar regions of the Northern and Southern hemispheres, at latitudes of 50 degrees or more.

Nacreous clouds are wave clouds, and are a cousin to the lenticular clouds that form over mountains. The stratosphere is very dry and it is rare for moisture to find it's way into this layer of the atmosphere. The ice crysals that form nacreous clouds are pushed up into the stratosphere by wave winds that are so strong they oscillate up through the trophosphere and into the stratosphere layer above.

Polar stratospheric clouds are made up of minuscule ice crystals, forming at around -85 degrees Celsius (-124 degrees Fahrenheit) Very cold indeed! They are typically seen in the winter months as the sun sets or rises and are illuminated by the suns rays from below the horizon.

The iridescent colours of nacreous clouds is due to the ice crystals being of a uniform shape and size and the cloud cover being thin. The sun has to be at just the right angle below the horizon to cause differaction and interference with the crystals to produce these beautiful colours.

What is the ozone layer? It is a delicate layer of oxygen formed naturally at about 20-30 miles (32 to 48 km) high in the stratosphere. It protects life on this planet from harmful ultraviolet light; over exposure to UV rays can lead to skin cancer for humans but would also cause other damaging affects to plants and animals. The ozone layer has been depleting in the Polar Regions (especially in the Antarctic) at about 4% a decade since it was first recorded in the 1970s.

Our modern lifestyle produces CFCs (chlorofluorocarbons), which are found in aerosols, fridges, solvents and much more besides. When CFCs are released into the atmosphere, they make their way up through to the stratosphere where they are converted by the sun's UV rays into chlorine compounds that in turn react with the ozone molecules leading to the depletion of the ozone layer.

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How Nacreous Clouds Affect the Ozone Layer

Beautiful but destructive clouds

Polar stratospheric clouds provide a surface for the chlorine and bromine in the CFC's to react into an active form, even if the forms of chlorine compounds are benign. This reaction makes the chlorine become destructive to the ozone layer. Simultaneously the ice crystals also remove nitrogen which helps slow and moderate the damaging chlorine and bromine.

Nacreous clouds help accelerate the process of the depletion of the ozone layer, without the clouds there is little or no damage.

Nacreous Cloud Spotted! 9 December 2012 - Aberdeenshire, Scotland

Many people visited this page after spotting an amazing nacreous cloud in Aberdeenshire on 9th December 2012, thank you to all of you who commented below. The photo of this beautiful cloud is shown below, courtesy of Thincat, via Wikimedia Commons

Have You Seen Nacreous Clouds? - Tell me about it!

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Frost flowers 2 years ago

Ufo clouds are made Is when a chain reaction happenes

In the sky

Garrett 3 years ago

Look up Geoengineering. I have "RARE" pics like that from The Dalles Oregon and Porterville CA. This is a cover up. These Geoengineered clouds are all over the globe. LOL does rare mean, seen daily?? Wake people and google- climate engineering and Geoengineering.

anonymous 5 years ago

saw one over Winchester, Hampshire this morning.

anonymous 5 years ago

saw some early evening Dec 9 over Kodiak Alaska

anonymous 5 years ago

I saw the cloud over Fraserburgh yesterday at about 16:30. An extraordinary beautiful cloud.

anonymous 5 years ago

They were visible over Portlethen Aberdeenshire from around 4pm for over an hour, had no idea what they were till I read an article in our local newspaper this morning, we took lots of photos.

anonymous 5 years ago

@anonymous: Me too! We are out in Banchory and it was about the same time- amazing!

anonymous 5 years ago

@anonymous: I saw some at the same time - They were in the west sky and beautifully illuminated by the setting sun. There was one giant one and a few wisps around it. We also saw some in late summer - similar place in the sky but much later in day (9pm-ish).

anonymous 5 years ago

I saw some in aberdeen Scotland today at about 4pm (just before the sun set) amazing to see i didn't know what i was seeing till i found this website!

anonymous 5 years ago

Saw some over mid Scotland today in the morning at full daylight. First seen about 9am still visible as I send this at 11am

anonymous 5 years ago

October 24, 2012 in Champaign Illinois-- spectacular! Do you want to see photo?

anonymous 5 years ago

Was in Marco Island, FL on 9/16/12. Saw a cloud that was colorful and it kept on changing colors as it moved. I never saw this before. My son is doing a project at school on Nacreous clouds. Now I know what I saw. It was beautiful. Thank God for children and their homework.

Pat Goltz 5 years ago

I live at about 33 degrees latitude. One morning, before sunrise, there was a test rocket fired at White Sands, New Mexico (probably). It made a contrail that zigged and zagged with the winds at different layers, and the contrail was nacreous. It was seen in many parts of southern Arizona. I got a few lousy pictures, but it was a thrill to see it.

Melhi 5 years ago

These clouds are breathtaking - (literally AND figuratively.)

anonymous 5 years ago

Looks like unicorn farts.

KReneeC 5 years ago

How very fascinating

coolgrey 6 years ago

Interesting and informative backed up by beautiful photography. I love your site. Cheers!

David Dove 6 years ago

other-worldly, thank you

lesliesinclair 6 years ago

stunning and scary

anonymous 6 years ago

Wish they were good for the environment cause they are quite beautiful

anonymous 6 years ago

How sad to learn that the beautiful Nacreous clouds are harmful to the ozone layer. Still, they are amazing!

sorana lm 6 years ago

Just beautiful.

BrickHouseFabrics 7 years ago

Would love to see them!

burgessvillian 7 years ago

Awesome pictures. Just learned something new again. I never knew of these clouds before. Thumbs up.

kimmanleyort 7 years ago

Another very interesting and beautiful lens. I think Dom has a good point - cloud art?

justholidays 7 years ago

I think they're beautiful and would look amazingly wonderful on my office walls! They look so quiet and delicate... Oh well, you know now that I love clouds ;)

callinsky lm 7 years ago

Beautiful lens as always, Lucy. I wasn't aware of the damage to the ozone either. Very interesting and scary at the same time.

SacredCynWear 7 years ago

Wow, this was a very interesting read. Who know that clouds could be so destructive. They are quite beautiful. This is a great lens, I love learning something new!

Indigo Janson 7 years agofrom UK

They look so beautiful, I never would have known about the threat they pose to the ozone layer. I love all of your 'natural wonders' series, we're lucky to have such informative and appealing guides to the natural phenomena around us.